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Projet DRAGON : Les grandes failles décrochantes chinoises
***Loads on the Earth Lithosphere at Different Spatial and Temporal Scales : Constraints from Space Geodesy and Satellite Imagery.
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Durée : 2012 - 2016
Coordinatrice : C. Lasserre
Equipe ISTerre impliquée :
– Cycle sismique et déformations transitoires
Collaborations internationales :
– Peking University (Dr Shen Zhenkang)
– Institute of Geology, China Earthquake Administration (Dr Sun Jianbao, Pr Xu Xiwei, Dr Liu-Zheng Jing)
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EXECUTIVE SUMMARY
With several major faults capable of producing devastating earthquakes, a large and high plateau bounded by prominent mountain ranges, and a fast rate of development, China is a rather unique place to study fault seismic cycle, continental deformation, tectonic-climate interactions, as well as human impact on ground deformation. Global, remote sensing data are well adapted to survey such phenomena with a wide variety of spatial wavelengths and temporal behaviors. The recent evolution toward higher resolution and time series analysis in satellite imagery and space geodesy (GPS, InSAR) provides new key observations that allow to refine or even revise our views on the lithosphere response to tectonic, hydrological or anthropic-related loading variations. Although covering only the past decades, space data also allow to jointly analyze short-term and long-term deformation and reconcile them through integrated models. We now stand at a turning point, with more progresses to expect from the new generation of satellite data.
This project builds on the experience gained from the past 2 Dragon projects (2577 and 5305), with both methodological and geophysical goals. The objective is to provide the most precise measurements of ground surface displacement, combining different, complementary techniques (high resolution optical images, GPS and InSAR), to constrain models of the lithosphere response to (WP1) stress and strain variations throughout the seismic cycle or to (WP2) nontectonic sources of load.
In (WP1), we aim in particular at detecting and analyzing lateral variations of coupling during the interseismic stress build up period along selected faults. This is important as coupling variations may influence not only earthquakes patterns on each fault (nucleation zone, rupture extent and arrest) but also the regional stress field, up to large distances from the fault. Starting from detailed InSAR studies at the scale of a fault system, we will merge GPS and InSAR data, exploiting at best their own specificities in terms of space and time resolution, into regional maps and models of the present-day elastic/anelastic deformation. More emphasis will be given on what’s going on at the margins of the Tibetan Plateau, where a lot of efforts were already focused on during Dragon 2.
In addition, to help documenting how coseismic slip distribute along faults, how it relates to fault segmentation, how it may evolves from one earthquake to another (paleoseismology from space), we intend to use high-resolution optical imagery to map all ranges of offsets of preserved morphological markers. This would complement any other co- (and post)- seismic studies of any event that would occur during this Dragon 3 project.
In (WP2), we propose to extract from the WP1 InSAR time series non tectonic signals related to hydrology (permafrost melting, aquifer pumping, water table changes), mining, or crustal rebound (due to ice sheet melting or lake water level fluctuations). This is critical for properly correcting thus interpreting GPS and InSAR-derived small displacement rates . It also brings information on the lithosphere rheology, that in turn can be used to model fault behaviour during the seismic cycle (WP1). We will primarily focus on the monitoring and modelling of the vertical deformation induced by water level fluctuations of large lakes in Tibet.
Most work will be done continuing to exploit the present archive of ERS, Envisat and ALOS SAR data, and available high resolution optical and multispectral imagery. Further improvement will be made to our own Small Baseline interferometric chain and time series analysis (NSBAS, Doin et al., 2011) to get prepared for the next step for InSARists : "absorbing" much larger data sets to come from Sentinel and ALOS-2.